There is known a handling system arranged a visual sensor at an upstream side of a belt conveyor, detecting an article (hereinafter described as a “workpiece”) conveyed by the belt conveyor, and using output data of the visual sensor to control an operation performed by a robot on the workpiece. For example, a handling system shown in the following Patent Document uses a visual sensor to capture an image of each workpiece conveyed by a belt conveyor, prepares data linked with each workpiece, and transmits the data to a robot controller. The robot controller prepares a database of received data and performs processing on a workpiece reaching a work position of the robot by conveyance by the belt conveyor based on the data read out from the above database.